This invention relates generally to apparatus for limiting radio frequency power and more particularly to apparatus for limiting microwave frequency power through the utilization of power absorbing ferrite material.
Ferrite power limiting devices utilizing the characteristic of subsidiary resonance are well known. One such device is taught in U.S. Patent 3,500,256 issued to P. S. Carter, et al. which additionally discloses the use of a series of dielectric resonators. This device, however, has an inherent problem in obtaining a large dynamic range, in excess of 20db, because of the use of small ferrite spheres disposed within each of the dielectric resonators. Accordingly, the ferrite volume necessary to limit RF signals over a broad power range is not available.
The coupled cavity transmission system using dielectric resonators of high dielectric constant can be tuned to form a structure which is adapted to increase the bandwidth capability; however, the reduction in volume from that of a metallic cavity raises the RF magnetic field, thus tending to lower the limiting level from that obtained in other prior art apparatus.
The principal disadvantage of conventional ferrite power limiters is their small dynamic range and their relatively high threshold powers. It is the purpose of the present invention, therefore, to provide a device which solves the present deficiencies and being adapted to selectively limit high level signals over a 15- 30% frequency bandwidth which will accordingly allow the ferrite limiters to be efficiently applied to communications in electronic warfare systems.